Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → Analytical Chemistry → Classical methods ↓


Gravimetric Analysis


Gravimetric analysis is a classical method used in analytical chemistry to determine the quantity of an analyte based on the measurement of mass. It is one of the most accurate and precise methods for quantitative analysis available in the field and is widely used in laboratories to analyze compounds. By focusing on the mass of a compound, this method can give very reliable results, often with an accuracy of up to four decimal places.

Introduction to gravimetric analysis

Gravimetric analysis involves converting the analyte (the substance being analyzed) into an insoluble precipitate. The precipitate is then collected by filtration, washed to remove impurities, converted into a stable form, and weighed. The mass of the desired component is then calculated from the measured mass of the precipitate and its known chemical composition.

Basic steps in gravimetric analysis

1. Preparation of the solution

The first step is to prepare a solution containing the analyte. It is important to completely dissolve the sample in a suitable solvent to ensure that the analyte is free to react in the next steps.

2. Rain

Next, a reagent is added to the solution to form an insoluble compound with the analyte. This process requires care to ensure that the precipitate is pure and crystalline, as these characteristics increase both accuracy and ease of filtration. The reaction used must be specific to the component being measured. For example, if chloride ions are to be measured, silver nitrate can be used as the reagent to form silver chloride, a solid:

Ag +(aq) + Cl -(aq) → AgCl(s)

3. Digestion

The precipitate is usually allowed to digest by placing it in a hot solution for a period of time. This process increases the size of the particles, reduces impurities and makes the filtration process easier. During digestion, smaller particles often dissolve and precipitate on larger particles again.

4. Filtration and washing

After digestion, the precipitate is separated from the solution by filtration. Typically, a paper or Gooch crucible equipped with a high-porosity ceramic disk is used. The precipitate is then washed with a pure solvent to remove any dissolved impurities, which could cause errors if they remained in the solid.

5. Drying and weighing

The precipitate is dried to eliminate any remaining solvent and brought to a constant mass by heating. When the mass becomes constant upon constant weighing, it is finally weighed. The accurate mass allows the amount of the analyte to be accurately calculated.

6. Calculations

The chemical formula and molar mass of the precipitate are used to calculate the amount of the analyte in the initial sample. Here is a simplified formula:

Mass of analyte = (Mass of precipitate) x (Molar mass of analyte component / Molar mass of precipitate)

Advantages of gravimetric analysis

Despite being a classical technique, gravimetric analysis offers several advantages:

  • High accuracy and precision: Since it is based on mass, it minimises the errors associated with instrumental calibration and can achieve a high level of precision.
  • Cost-effectiveness: Minimal equipment is required other than basic laboratory equipment.
  • General applicability: The precipitation reaction can be used for a wide range of substances by adjusting the reaction.

Limitations of gravimetric analysis

However, some limitations should be considered:

  • Time-consuming: This process involves multiple steps, requiring patience and precise technique to ensure accuracy.
  • Selective conditions: Sometimes specific conditions are required for precipitation, such as pH control.
  • Need for a pure sample: Impurities in the sample can cause errors, especially if they co-precipitate with the analyte.

Visual example: gravimetric analysis process

Gravimetric Analysis Procedure Prepare the Solution Sediment Dry and weigh Filter Calculations

Applications of gravimetric analysis

Gravimetric methods are used in various fields:

  • Pharmaceutical industry: For quality control and determination of substances in pharmaceuticals.
  • Environmental testing: Used to determine the concentrations of pollutants in water, soil, and air samples.
  • Food industry: Calculating moisture content, fat and other ingredient levels in food products.

Common types of gravimetric analysis

Several gravimetric techniques are commonly applied:

  • Evaporation gravimetry: where the analyte is vaporized leaving a residue or is measured by the loss in mass itself.
  • Precipitation gravimetry: The classic method described above, in which the analyte forms an insoluble compound.

Conclusion

Gravimetric analysis, focusing on mass and method-specific analysis, remains a fundamental practice in analytical science. Although it is technically simpler than some modern methods, it continues to be used because of its accuracy, relatively low cost, and ability to produce highly accurate results.


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Gravimetric Analysis

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